Method and apparatus for cancelling an interference in wireless communication system

ABSTRACT

A method and an apparatus for cancelling interference in a wireless communication system are provided. The method includes acquiring interference signal information on a reception signal received from a base station based on a preconfigured constellation set, and cancelling an interference signal from the reception signal by using the acquired interference signal information. Accordingly, reception performance in a cell edge can be improved by acquiring dominant interference signal information.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under 35 U.S.C. § 119(a) of a Koreanpatent application filed on Feb. 28, 2013 in the Korean IntellectualProperty Office and assigned Serial number 10-2013-0022242, the entiredisclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a wireless communication system. Moreparticularly, the present disclosure relates to a method and apparatusfor cancelling interference in a wireless communication system.

BACKGROUND

Generally, a wireless communication system has been developed toguarantee user's activity and provide a voice service. However, thewireless communication system has gradually expanded its scope ofservice to include a data service besides voice service, and, in recentyears, the wireless communication system has developed to a high speeddata service. However, in the wireless communication system providingcurrent services, since resources have become insufficient and userswant much higher speed services, more developed wireless communicationsystem are required.

To satisfy these needs, the standardization of Long Term Evolution(LTE), which is one of the systems developed as next generation wirelesscommunication system, is ongoing in the 3rd Generation PartnershipProject (3GPP).

Long Term Evolution (LTE) technology implements high speed packet basedcommunication supporting maximum 100 Mbps transmission speed. To thisend, various methods are discussed. For example, there is a method ofreducing the number of nodes positioned on the communication path bysimplifying a network structure or a method of approaching wirelessprotocols to wireless channel as close as possible.

In the Multiple-Input Multiple-Output-Orthogonal Frequency-DivisionMultiple Access (MIMO-OFDMA) wireless communication system like the LTE,a terminal receives information only for demodulating data from aserving base station. However, in the area like cell edge, where aninterference signal is strongly received from an adjacent base station,if the terminal knows about the information on the interference signal,the terminal can improve its reception performance by handling (jointdetection, interference cancellation, and the like) the information.However, in general, there are many different kinds of information ofinterference signals to improve a terminal's reception performance.Therefore, the complexity of a method to find out the many differentkinds of interference signal information can be increased.

Accordingly, a study of acquiring interference signal information withlow complexity is required to enhance a terminal's receptionperformance.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method and apparatus for cancellinginterference in a wireless communication system without support from aserving base station.

The present disclosure may further provide a method and apparatus forforming a constellation set (pattern) corresponding to a pattern ofinterference signal interference in a wireless communication system, andcancelling the interference signal based on the constellation set.

In accordance with an aspect of the present disclosure, a method ofcancelling interference of a terminal in a wireless communication systemis provided. The method includes acquiring interference signalinformation on a reception signal received from a base station based ona preconfigured constellation set, and cancelling an interference signalfrom the reception signal by using the acquired interference signalinformation.

In accordance with another aspect of the present disclosure, a terminalfor cancelling an interference signal in a wireless communication systemis provided. The terminal includes a wireless communication unitconfigured to transmit and receive a signal with a base station, astorage unit configured to store a constellation set including at leastone constellation corresponding to a pattern of interference signal, anda controller configured to acquire interference signal information on areception signal received from the base station, and cancel theinterference signal from the reception signal by using the acquiredinterference signal information, based on the constellation set.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram illustrating time and frequency resources in LongTerm Evolution (LTE)/Long Term Evolution-Advanced (LTE-A) systemaccording to an embodiment of the present disclosure;

FIG. 2 is a diagram illustrating one sub-frame and one resource block(RB) which is a minimum unit for downlink scheduling in an LTE/LTE-Asystem according to an embodiment of the present disclosure;

FIG. 3 is a diagram illustrating a normal terminal's data receptionmethod in a cell edge area according to an embodiment of the presentdisclosure;

FIG. 4 is a diagram illustrating a terminal's data reception methodaccording to an embodiment of the present disclosure;

FIGS. 5A, 5B, 5C, 5D and 5E are diagrams illustrating a free codingconstellation set which can be combined according to an embodiment ofthe present disclosure;

FIG. 6 is a flowchart illustrating a process of acquiring interferencesignal information by a terminal according to an embodiment of thepresent disclosure; and

FIG. 7 is a block diagram illustrating an internal structure of aterminal according to an embodiment of the present disclosure.

The same reference numerals are used to represent the same elementsthroughout the drawings.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

Herein, a method for acquiring interference signal information isdescribed as an example of a Long Term Evolution (LTE)/Long TermEvolution-Advanced (LTE-A) system, but it is not limited thereto. Themethod can be applied to the other wireless communication systems havingsimilar technical features.

FIG. 1 is a diagram illustrating time and frequency resources in anLTE/LTE-A system according to an embodiment of the present disclosure.

Referring to FIG. 1, the wireless resources that a base stationtransmits to a terminal is divided by a Resource Block (RB) unit in afrequency axis, and by a subframe unit in a time axis.

Generally, the RB includes 12 subcarriers, and occupies 180 kHzbandwidth in an LTE/LTE-A system. On the other hand, generally, thesubframe includes 14 OFDM symbol sections in an LTE/LTE-A system, andoccupies 1 msec time section.

When performing scheduling in an LTE/LTE-A system, resources may beallocated by a subframe unit in a time axis, and by an RB unit in afrequency axis.

FIG. 2 is a diagram illustrating one sub-frame and one resource block(RB) which is a minimum unit for downlink scheduling in an LTE/LTE-Asystem according to an embodiment of the present disclosure.

Referring to FIG. 2, wireless resources are configured with one subframein a time axis, and one RB in a frequency axis. Such wireless resourcesinclude 12 subcarriers in a frequency domain and 14 OFDM symbols in atime domain, so that the wireless resources have 168 unique frequencyand time positions.

In LTE/LTE-A, each unique frequency and time position of FIG. 2 iscalled a Resource Element (RE). In addition, one subframe is configuredwith 2 slots while each slot includes 7 OFDM symbols.

A plurality of different kinds of signals can be transmitted to wirelessresources illustrated in FIG. 2.

Cell Specific RS (CRS) is a reference signal which is transmitted forall terminals belong to one cell.

Demodulation Reference Signal (DMRS) is a reference signal which istransmitted for a specific terminal.

Physical Downlink Shared Channel (PDSCH) is a downlink data channel usedby base station so as to transmit traffic to a terminal, and the trafficis transmitted by using RE to which reference signal is not transmittedin the data region of FIG. 2.

Channel Status Information Reference Signal (CSI-RS) is a referencesignal which is transmitted for the terminals belonging to one cell, andused for measuring channel status between terminal and base station. Inthis case, a plurality of CSI-RSs can be transmitted to one cell.

Other control channels (PHICH, PCFICH, PDCCH) provide controlinformation necessary for receiving PDSCH by a terminal, or transmitACK/NACK for operating HARQ for uplink data transmission.

FIG. 3 is a diagram illustrating a normal terminal's data receptionmethod in a cell edge area according to an embodiment of the presentdisclosure.

A serving cell 320 provides a service to a terminal 310, and, to thisend, the terminal 310 transmits/receives control information and datato/from the serving cell 320. In a general MIMO-OFDMA system including3GPP LTE, the terminal receives only information for demodulating datawhich is allocated to itself from a serving cell.

Meanwhile, an interference cell 330, which interferes with terminal 310,can be located close to the serving cell 320. In this case, a signalthat the interference cell 330 transmits to other terminals located inthe interference cell's own service coverage can be also received byterminal 310. In this case, the signal operates as interference for theterminal 310.

Generally, since the terminal 310 does not have information on theinterference signal transmitted from the interference cell 330 and thebase station does not transmit information on the interference, theterminal 310 is limited on improving a performance of the receivingsignal from the serving cell 320. Therefore, if the terminal 310 is ableto know information of the inter-cell interference signal, the terminalhaving an advanced receiver can improve performance in the cell edge byusing an inter-cell interference signal with the method of jointdetection or interference cancellation, and the like, when demodulatinga serving signal.

However, since there are so many different kinds of information oninterference signals that should be known, the method for finding outthe different kinds of information becomes more complicated affectingthe performance of the system.

In 3GPP LTE, the terminal should know the information such as atransmission mode of the interference signal, the number of layer, themodulation order of the signal, and the precoding matrix, and the like,when performing joint detection of a dominant interference signal andits own signal to improve performance in the cell edge.

If the terminal does not know any information among them, there are anumber of cases such as a multiple of transmission mode, the number oflayer, modulation order, and the number of precoding matrix, thatterminal should attempt to cancel an interference signal considering allthe number of cases.

However, if the terminal attempts to cancel an interference signalconsidering all the number of cases, complexity becomes too high andprocessing time can be delayed.

Problems of the related art are summarized as follows.

1. The related art detects a signal only by using information on aserving signal provided by a serving base station, such that theperformance of terminal degrades in the cell edge which is stronglyaffected by inter-cell interference.

2. The related art has a limitation of improving performance bywhitening a colored noise because there is no information of aninterference signal.

3. Acquiring interference signal information has a problem of highcomplexity because there are so many numbers of configurations of aninterference signal that can occur.

The present disclosure has been made in view of the above problems, andmore particularly, the present disclosure suggests a method of acquiringinterference signal information having low complexity for improving aterminal's reception performance in the cell edge.

In particular, a terminal according to the present disclosure mayacquire interference signal information based on a predetermined set (orpattern) of a constellation without a base station's assistance, andcancel an interference signal.

According to an embodiment of the present disclosure, a terminal mayacquire interference signal information based on a set of constellationswhich are configured with a precoded symbol (hereinafter, it will beused together with a precoding symbol) unit.

FIG. 4 is a diagram illustrating a terminal's data reception methodaccording to an embodiment of the present disclosure.

A serving cell 420 provides a service to a terminal 410 of the presentdisclosure in a cell edge area. The terminal 410 may transmit/receivecontrol information and data to/from the serving cell 420. In this case,the terminal 410 may be interfered by the interference cell 430 which isan adjacent cell.

The terminal 410 according to an embodiment of the present disclosuremay acquire interference signal information without the assistance of aserving base station, and decode a serving signal transmitted from theserving cell 420 by using the acquired interference signal information.To this end, the terminal 410 may previously configure a set ofconstellations (or, a precoding symbol constellation set, hereinafter,used together) which correspond to the pattern of an interferencesignal. In addition, the terminal 410 may classify the interferencesignal not by a modulation symbol unit but by a precoding symbol unit,then the terminal 410 may acquire interference signal information bycomparing the precoding symbol constellation set and the interferencesignal of the precoding symbol unit.

Hereinafter, the method for acquiring interference signal informationwithout assistance of a serving base station or an adjacent base stationis described in detail.

If a dominant interference signal is strongly received at the cell edge,it is possible to improve the reception performance of the terminal bydetecting an interference signal component. However, this interferencesignal information is not the information which is given by the basestation. Therefore, the terminal should find out necessary information.To this end, the terminal should know a transmission method, the numberof layers of a transmission signal, the precoding information and themodulation method in the MIMO-OFDMA system.

In case of 2×2 MIMO interference signal, the number of transmissionlayer (L) may be 1 or 2, accordingly, the received signal may beexpressed like Equation 1.

$\begin{matrix}{\begin{matrix}{{y = {{H\; P_{1}x} + n}},{{{when}\mspace{14mu} L} = 1}} \\{{= {{{\begin{bmatrix}H^{00} & H^{01} \\H^{10} & H^{11}\end{bmatrix}\begin{bmatrix}P_{1}^{0} \\P_{1}^{2}\end{bmatrix}}x} + \begin{bmatrix}n^{0} \\n^{1}\end{bmatrix}}},}\end{matrix}\begin{matrix}{{y = {{H\; P_{2}x} + n}},{{{when}\mspace{14mu} L} = 2}} \\{{= {{{\begin{bmatrix}H^{00} & H^{01} \\H^{10} & H^{11}\end{bmatrix}\begin{bmatrix}P_{2}^{00} & P_{2}^{01} \\P_{2}^{10} & P_{2}^{11}\end{bmatrix}}\begin{bmatrix}x^{0} \\x^{1}\end{bmatrix}} + \begin{bmatrix}n^{0} \\n^{1}\end{bmatrix}}},}\end{matrix}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Where y is a received signal, n is a noise, H is 2×2 channel matrix, Pnis a precoding matrix of rank n, and x is modulated symbol vector.

Since there are so many unknown parameters which should be known foreach of the above variables, complexity should be considerablyincreased, when totally classifying the transmission method ofinterference signal, the number of layer for transmission signal, theprecoding information and the modulation method.

The present disclosure performs a joint detection which handlesinterference signal in a symbol level, and a classification ofinterference signals for symbol-level advanced receivers such as asymbol-level cancellation.

To this end, according to an embodiment of the present disclosure, thetransmission method of an interference signal, the number of layers of atransmission signal, the precoding information, and the modulationmethod are not individually classified, but classified as combinedinformation.

That is, the combined information is not classified by the symbol of atransmitted modulation order but by using the precoded modulation symbol(precoding symbol) as following Equation 2.

$\begin{matrix}\begin{matrix}{{y = {{H\overset{\sim}{x}} + n}},} \\{{= {\begin{bmatrix}H^{00} & H^{01} \\H^{10} & H^{11}\end{bmatrix}\begin{bmatrix}{\overset{\sim}{x}}^{0} \\{\overset{\sim}{x}}^{1}\end{bmatrix}}},} \\{= \left\{ \begin{matrix}{{\begin{bmatrix}H^{00} & H^{01} \\H^{10} & H^{11}\end{bmatrix}\begin{bmatrix}{P_{1}^{0}x} \\{P_{1}^{1}x}\end{bmatrix}},} & {{{when}\mspace{14mu} L} = 1} \\{{\begin{bmatrix}H^{00} & H^{01} \\H^{10} & H^{11}\end{bmatrix}\begin{bmatrix}{{P_{2}^{00}x^{0}} + {P_{2}^{01}x^{1}}} \\{{P_{2}^{10}x^{0}} + {P_{2}^{11}x^{1}}}\end{bmatrix}},} & {{{when}\mspace{14mu} L} = 2}\end{matrix} \right.}\end{matrix} & {{Equation}\mspace{14mu} 2}\end{matrix}$

The present disclosure may acquire interference signal information in aprecoding symbol unit expressed in the form of px in the Equation 1, anduse the acquired interference signal information for a joint detection.As mentioned above, when performing the joint detection for the servingsignal and the interference signal classified in a precoding symbolunit, the precoded symbol may be used as Equation 3.

$\begin{matrix}\begin{matrix}{{y = {H_{eq}x_{eq}}},} \\{= {\begin{bmatrix}{H_{d}P_{n}} & H_{i}\end{bmatrix}\begin{bmatrix}x_{d} \\{\overset{\sim}{x}}_{i}\end{bmatrix}}}\end{matrix} & {{Equation}\mspace{14mu} 3}\end{matrix}$

As expressed above, when the joint detection is performed by using theclassified interference signal (i.e., precoded symbol), the Log LikehoodRatio (LLR) may be calculated as following Equation 4.

$\begin{matrix}\begin{matrix}{L_{1,n} = {{\ln{\sum\limits_{x_{i} \in {??}_{m}^{2}}{\sum\limits_{x_{d} \in {??}_{d,{+ 1}}^{2}}{{\exp\left( {{- \frac{1}{\sigma^{2}}}{{y - {H_{{eq},d}x_{d}} - {H_{i}{\overset{\sim}{x}}_{i\;}}}}^{2}} \right)}{P\left( {\overset{\sim}{x}}_{i\;} \right)}}}}} -}} \\{\ln{\sum\limits_{x_{i} \in {??}_{m}^{2}}{\sum\limits_{x_{d} \in {??}_{d,{- 1}}^{2}}{{\exp\left( {{- \frac{1}{\sigma^{2}}}{{y - {H_{{eq},d}x_{d}} - {H_{i}{\overset{\sim}{x}}_{i\;}}}}^{2}} \right)}{P\left( {\overset{\sim}{x}}_{i\;} \right)}}}}} \\{= {{\max\limits_{{x_{i} \in {??}_{m}^{2}},{x_{d} \in {??}_{d,{+ 1}}^{2}}}\left\{ {{{- \frac{1}{\sigma^{2}}}{{y - {H_{{eq},d}x_{d}} - {H_{i}{\overset{\sim}{x}}_{i\;}}}}^{2}} + {\ln\;{P\left( {\overset{\sim}{x}}_{i\;} \right)}}} \right\}} -}} \\{\max\limits_{{x_{i} \in {??}_{m}^{2}},{x_{d} \in {??}_{d,{- 1}}^{2}}}\left\{ {{{- \frac{1}{\sigma^{2}}}{{y - {H_{{eq},d}x_{d}} - {H_{i}{\overset{\sim}{x}}_{i\;}}}}^{2}} + {\ln\;{P\left( {\overset{\sim}{x}}_{i\;} \right)}}} \right\}}\end{matrix} & {{Equation}\mspace{14mu} 4}\end{matrix}$

Where, Ll,n is LLR of nth bit of first stream, s2 is noise variance, isa prior distribution of {tilde over (x)}_(i) and can be previouslycalculated on the assumption that each modulation order is equiprobable.Sm is a constellation point set of precoded symbols set m, C2d isconstellation point set of a desired symbol vector, C2d,α is symbolvector set satisfying bl,n=α.(bl,n is n-th bit of 1-th stream).

It will be described as an example that a base station having 2Txantenna and a terminal having 2Rx antenna perform the joint detection ofa serving signal and a dominant interference signal in an LTE system.

It is assumed that the number of cases for information that the dominantinterference signal can have is expressed as following in Table 1.

TABLE 1 Transmission mode: 2, 3, 4, 6 The number of layer: 1 or 2Modulation order: QPSK or 16QAM

According to the above assumption, combinable precoding symbols for theinterference signal may be expressed by 5 kinds (pattern) of precodingsymbol constellation sets illustrated in FIGS. 5A to 5E.

FIGS. 5A and 5B are constellations in case of 1 layer, FIG. 5C, 5D, and5E are constellations in case of 2 layers according to an embodiment ofthe present disclosure.

FIG. 5A is a constellation when QPSK is used for modulation order, andFIG. 5B is a constellation when 16 QAM is used for modulation order.

FIG. 5C is a constellation when QPSK is used for each layer, FIG. 5D isa constellation when QPSK and 16 QAM are used for each layer, and FIG.5E is a constellation when 16 QAM is used for each layer.

According to the assumptions of Table 1, combinable precoding symbol ofinterference signal corresponds to one of 5 sets of constellationdefined in the sets of precoding symbol constellations.

Therefore, according to an embodiment of the present disclosure foracquiring interference signal information in a precoding symbol unit,complexity can be reduced (from 16 to 5) compared with the number ofcases(4*2+4*4=24) when interference signal is acquired in a modulationsymbol unit.

FIG. 6 is a flowchart illustrating a process of acquiring information ofan interference signal by a terminal according to an embodiment of thepresent disclosure.

First, the terminal may receive a signal at operation 610. The signalreceived by the terminal may include a serving signal to be receivedfrom a serving cell, and an interference signal interfered by aninterference cell.

The terminal may acquire serving signal information at operation 620.The reason for such is that the terminal is to acquire an interferencesignal component by canceling the serving signal from the receivedsignal.

At the operation where the terminal classifies dominant interferencesignal, the serving signal has only information such as modulationorder, and the like, but the actually transmitted symbol is not detectedyet. Accordingly, in order to cancel the serving signal from thereceived signal, the terminal only can use the information such asmodulation order, and the like. In this case, there may be two methodsas follows.

First method is to use serving data signal (soft cancellation).

This method may be used in a case in which the decoding/detection isperformed, firstly, only by using the serving signal not by jointdetection, and then, the joint detection is performed after thedetection fails. That is, after the non-joint detection/decoding isperformed first, a soft symbol is regenerated by using the decoderoutput to cancel each other. The optimal interference classificationaccording to above method is expressed as Equation 5.

$\begin{matrix}{\hat{m} = {\underset{m \in \mathcal{M}}{argmax}\left\{ {\prod\limits_{k = 1}^{K}\;{\sum\limits_{\overset{\sim}{x_{i}} \in {??}_{m}^{2}}\;{\frac{1}{\left( {\pi\sigma}^{2} \right)^{2}}{\exp\left( {{- \frac{1}{\sigma^{2}}}{{{\overset{\sim}{Y}(k)} - {{H_{i}(k)}{\overset{\sim}{x}}_{i}}}}^{2}} \right)}{P\left( \overset{\sim}{x} \right)}}}} \right\}}} & {{Equation}\mspace{14mu} 5}\end{matrix}$

Where, {tilde over (Y)}(k) is a received signal in k-th subcarrier aftercanceling a soft regeneration of desired signal, K is the number ofsample for classification, and P({circumflex over (x)}) is a priordistribution of {tilde over (x)} and can be previously calculatedoffline.

Secondly, a method of using a reference signal in the serving cell maybe considered. Minimizing a residual error by perfectly accomplishing acancellation of a serving signal may be favorable to interference signalclassification. For this reason, the terminal may use the referencesignal of the serving cell (e.g., common reference signal, CRS) that theterminal perfectly knows. When using the above method, the interferencesignal classification may be performed only in the resource element (RE)where serving CRS is located. For reference, according to LTE systemstandards, CRS symbols which are transmitted from 2 Tx antenna arelocated in the 12 REs in the PDSCH region expect the PDCCH region within1 RB. The optimal interference signal classification according to abovemethod is expressed as Equation 6.

$\begin{matrix}{\hat{m} = {\underset{m \in \mathcal{M}}{argmax}\left\{ {\prod\limits_{k = 1}^{12}{\sum\limits_{\overset{\sim}{x_{i}} \in {??}_{m}^{2}}\;{\frac{1}{\left( {\pi\sigma}^{2} \right)^{2}}{\exp\left( {{- \frac{1}{\sigma^{2}}}{{{Y(k)} - {{H_{d}(k)}{s_{d}(k)}} - {{H_{i}(k)}{\overset{\sim}{x}}_{i}}}}^{2}} \right)}{P\left( \overset{\sim}{x} \right)}}}} \right\}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$

Where, Sd(k) is k-th CRS symbol vector of serving cell in 1 RB.

After acquiring serving signal information by using one of the abovementioned two methods, the terminal proceeds to operation 630, anddetects an interference target signal by canceling the serving signalfrom the signal received at the previous operation. Here, theinterference target signal is a sampled signal to finally acquiredominant interference signal.

Then, the terminal proceeds to operation 640, and checks the precodingsymbol constellation set. The precoding symbol constellation set mayhave a combinable constellation as an element by using an inputparameter such as transmission mode information, layer information, andmodulation order information. The precoding symbol constellation set maybe provided (stored) by the terminal itself, but may also be receivedfrom the service provider.

After that, the terminal proceeds to operation 650, and compares theinterference target signal, excluding the serving signal from thereceived signal, with the stored precoding symbol constellation set. Theterminal determines whether the constellation corresponding to theinterference target signal exists in the precoding symbol constellationset at operation 660. Here, the finding of a corresponding constellationmay correspond to finding the constellation having a signal distributionthat is closest to the signal distribution of interference targetsignal.

When the constellation exists, the terminal proceeds to operation 670,and acquires information on dominant interference signal according tothe constellation which corresponds (mapped) to the interference targetsignal. In this case, the information on dominant interference signalacquired by the terminal may include the information related to thetransmission mode, the layer, the modulation order, and the precodingmatrix.

The terminal proceeds to operation 680, and decodes the received signalbased on the acquired information on dominant interference signal. Inthis case, the terminal may use the methods such as the joint detection,the interference cancellation, and the like so as to decode the receivedsignal.

FIG. 7 is a block diagram illustrating an internal structure of aterminal according to an embodiment of the present disclosure.

As illustrated in FIG. 7, the terminal of the present disclosure mayinclude a wireless communication unit 710, a storage unit 720, and acontroller 730.

The wireless communication unit 710 may perform a function oftransmitting/receiving a corresponding data for a wireless communicationterminal. The wireless communication unit 710 may include a RFtransmitter which performs up conversion and amplification of afrequency of a transmitted signal, and a RF receiver which performs alow-noise amplification of the received signal and down-conversion ofthe frequency of the received signal. Moreover, the wirelesscommunication unit 710 may receive data through a wireless channel tooutput to a controller 730, and transmit data outputted from thecontroller 730 through the wireless channel.

The storage unit 720 may perform a function of storing a program anddata necessary for the operation of the terminal, and be divided into aprogram area and a data area. The storage unit 720 according to anembodiment of the present disclosure may further include a precodingsymbol constellation set storage area 721 storing a precoding symbolconstellation set including at least one constellation which correspondsto the pattern of interference signal.

The controller 730 may control a signal flow between blocks so that theterminal may be operated according to an embodiment of the presentdisclosure. Particularly, the controller 730 may control consecutiveprocedures of acquiring interference signal information on the terminalby previously configuring the precoding symbol constellation set whichcorresponds to the pattern of interference signal, classifying theinterference signal not by modulation symbol unit but by precodingsymbol unit, and comparing the precoding symbol constellation set withthe interference signal of the precoding symbol unit.

To this end, the controller 730 may further include an interferencesignal information acquiring unit 731 and a decoding unit 732.

The interference signal information acquiring unit 731 may acquireinterference signal information based on the precoding symbolconstellation set stored in the storage unit 720, particularly, in theprecoding symbol constellation set storage area 721. According to anembodiment of the present disclosure, the acquired interference signalinformation may be precoded symbol unit.

Particularly, the interference signal information acquiring unit 731 mayacquire interference target signal by canceling the serving signal fromthe received signal, and checking the constellation which corresponds tothe interference target signal by comparing the interference targetsignal with the precoding symbol constellation set. The interferencesignal information acquiring unit 731 may determine the informationaccording to the checked constellation as interference signalinformation.

In this case, the interference signal information acquiring unit 731 maycancel the serving signal from the received signal by using thereference signal of a serving cell. Alternatively, the interferencesignal information acquiring unit 731 may regenerate the serving signalby using a result of decoding processing when there is the result ofdecoding processing, and cancel the regenerated serving signal from thereceived signal by using the regenerated serving signal.

The decoding unit 732 may receive information on an interference signalacquired from the interference signal information acquiring unit 731 anddecode the received signal. The information on the interference signalmay be a precoded symbol unit and include transmission mode informationof a precoded symbol, layer information, and modulation orderinformation, and the like.

The decoding unit 732 may use the methods such as the joint detection,the interference cancellation, and the like so as to decode a receivedsignal.

According to the present disclosure, the terminal may acquire dominantinterference signal information in the cell edge and improve itsreception performance by using an advanced receiver such as the jointdetection, the interference cancellation, and the like. In addition, theimprovement of reception performance of a terminal in the cell edge maylead to the increase of the system throughput. Further, according to thepresent disclosure, without changing the conventional system standard ofan LTE system, the reception performance of a terminal in the cell edgemay be improved.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method by a terminal in a wirelesscommunication system, the method comprising: storing a pre-configuredconstellation set: receiving a signal from a base station; identifying aconstellation among the pre-configured constellation set by selectingthe constellation having a closest signal distribution with aninterference target signal, the interference target signal beingacquired by canceling a serving signal from the received signal;acquiring interference signal information on the received signal basedon the identified constellation; and cancelling an interference signalfrom the received signal by using the acquired interference signalinformation.
 2. The method of claim 1, wherein the pre-configuredconstellation set includes at least one constellation which correspondsto a pattern of the interference signal.
 3. The method of claim 1,wherein the acquiring of the interference signal information comprisesacquiring interference signal information in a pre-coded symbol unit. 4.The method of claim 1, wherein the identifying of the constellationamong the pre-configured constellation set comprises: comparing a signaldistribution of the interference target signal with each signaldistribution of the pre-configured constellation set.
 5. The method ofclaim 1, wherein the acquiring of the interference target signalcomprises cancelling the serving signal from the received signal byusing a reference signal of a serving cell.
 6. The method of claim 1,wherein the acquiring of the interference target signal furthercomprises: regenerating the serving signal by using a result of decodingprocessing if the result of decoding processing exists; and cancellingthe regenerated serving signal from the received signal by using theregenerated serving signal.
 7. The method of claim 1, wherein thepre-configured constellation set is configured based on a combination ofat least two of transmission mode information, layer information,precoding information and modulation order information.
 8. A terminal ina wireless communication system, the terminal comprising: a wirelesscommunication unit configured to transmit and receive signals with abase station; a storage unit; and a controller configured to: store apre-configured constellation set, control the wireless communicationunit to receive a signal from the base station, identify a constellationamong the pre-configured constellation set by selecting theconstellation having a closest signal distribution with an interferencetarget signal, the interference target signal being acquired bycanceling a serving signal from the received signal, acquireinterference signal information on the received signal based on theidentified constellation, and cancel the interference signal from thereceived signal by using the acquired interference signal information.9. The terminal of claim 8, wherein the pre-configured constellation setincludes at least one constellation which corresponds to a pattern ofthe interference signal.
 10. The terminal of claim 8, wherein thecontroller is further configured to: compare a signal distribution ofthe interference target signal with each signal distribution of thepre-configured constellation set.
 11. The terminal of claim 8, whereinthe controller is further configured to cancel the serving signal fromthe received signal by using a reference signal of a serving cell. 12.The terminal of claim 8, wherein the controller is further configuredto: regenerate the serving signal by using a result of decodingprocessing when the result of decoding processing exists; and cancel theregenerated serving signal from the received signal by using theregenerated serving signal.
 13. The terminal of claim 8, wherein thepre-configured constellation set is configured based on a combination ofat least two or transmission mode information, layer information,precoding information and modulation order information.
 14. A method ofin a wireless communication system, the method comprising: storing apre-configured constellation set; receiving a signal including a servingsignal and an interference signal; acquiring serving signal informationfrom the serving signal; cancelling the serving signal from the receivedsignal; identifying a constellation set among the pre-configuredconstellation set by selecting the constellation having a closet signaldistribution with an interference target signal, the interference targetsignal being acquired by canceling the serving signal from the receivedsignal; acquiring interference signal information on the received signalbased on the identified constellation; and decoding the received signalbased on the acquired interference signal information.
 15. The method ofclaim 14, wherein the pre-configured constellation set is generatedbased on a combination of at least two of transmission mode information,layer information, precoding information and modulation orderinformation.
 16. A non-transitory computer readable medium for storing acomputer program of instructions configured to be readable by at leastone processor for instructing the at least one processor to execute acomputer process for performing the method of claim
 14. 17. Anon-transitory computer readable medium for storing a computer programof instructions configured to be readable by at least one processor forinstructing the at least one processor to execute a computer process forperforming the method of claim 1.